I really don't understand this. This problem just randomly appeared about 2 weeks ago. Under WOT open throttle in pretty much any gear, or moderate throttle in 3rd/4th gear, I can hear what sounds like metallic popcorn coming from my engine bay. I've always used 93 octane and it's been really cold here lately. The mixture still looks rich based on my A/F gauge (Autometer Led style), and even with a gallon of toulene in the mix, it still pings all the same. Any one have suggestions?

 

Assuming this is a Turbo II. When was your last full tuneup. When was the fuel filter last changed?

 

New motor only with 12K miles on it, fuel filter was changed with it. It's an '87 TII. (Which should habve been in my sig....hmmmm)

 

Maybe check the CAS timing.

Also check the knock sensor function.
It's supposed to retard the timing when it hears knocks.

Does toluene affect the octane rating?
Does it affect the O2 sensor?

 

I haven't rechecked the timing, but I don't see why it would have changed in recent weeks.

As for the toulene, it does increase octane...one gallon should raise it to a little over 94 with a full tank of gas.

 

Timing looks good to me and I just changed the fuel filter. Could a faulty ECU have anything to do with this?

 

****, im having the same problem, are you sure its detonation? it only happens to me when im in 3rd-5th at low rpm, then go wot, and the boost goes up above 5 psi

 

so is this definatly detonation? ive heard that det sounds like someone hitting the motor with a hammer or some **** like that, so im not sure if it is or not.

 

check your plugs and make sure there not fould out

 

YOu getting gas at the same place? YOu could be getting bad gas.

Maybe you should try some octane booster until you solve the problem.

 

Tried octane booster(toulene) and that didn't help the problem.
I haven't checked the plugs, but why would a fouled plug cause detonation, would that just cause the car to be sluggish and hesistate?

 

Fouled plugs indicate excess carbon buildup on the rotor face.
When the carbon buildup starts to crack loose the new edges of carbon flakes can get red hot, which will pre-ignite the charge.
That's more of a long shot.

I'd start by checking the timing.
Then while the timing light is on, check the knock sensor.

 

It happend to my friends car, thats why i suggested it.

 

ive got the EXACT same problem.

changing the plugs fixed it for a few days and now it's back!

 

Sureshot beat me to it.
You can have a dirty fuel injector (they don't anyways show up on o2 sensors, honestly) But I'd say that you're engine is carboned up. Clean the plugs, check the timing, and clean out the inside of your engine with whatever method is accepted this week .
Don't wait till next week because the method will change, lol.

 

if you change plugs and the car is ok then a few days later the problem returns it's likely an ignition issue...check coil packs and plug wires. Also, try another AFM (I've always had many for RX-7's that are good though some run or idle better than others, these things are old hehe).

 

I had the same problem. Changed the plugs and it went away then it came back. Ngk spark plug wires cleared that up and it ran very smooth. What wires are you running?

 

what size wires would you recommend?

 

8mm

 

so whats the best way of cleaning out the carbon build up this week?

 

What boost are ya running? cone filter, 3" downpipe, open exhaust (assume no cats) and an FCD in cold weather is a recipe for too much boost -> detonation.

-Henrik

 

Pinging starts at between 2-5 psi, depending on load. I've run the car all the way up to 14 psi before with zero problem. I'm starting to think the ECU is all kinds of f'ed up. I was looking a little closer to the A/F gauge, and the car goes really lean every now and then for a very short period of time. It's kinda wierd.

 

um, i just took my plugs out to check them, and the rear trailing plug looks to be fubared. the elctrode looks like it has been melted off about halfway down, and the middle of the elctrode is indented, like a crater or something. the carbon deposits on both trailing plugs are a dark tan, while the leading plugs have black carbon deposits. could this be my problem? what could have caused it? the plugs are NKG hot platnium, i got them from mazdatrix i think.

 

I think the injectors have a common ground under the UIM.

I'd recheck all grounds..

 

So your running up to 14psi with no fuel mods?? Get an SAFC or something so u can give it more fuel. Thats probably why your plugs are so burnt up becaise its running lean.